The present invention relates to a display system where polarized light from a display impinges on a platelike laminate at Brewster""s angle or emerges therefrom at an angle equal to Brewster""s angle. This display system can be used as a head-up display system which allows, for example, the driver of a car to view vehicular information, while looking out a front windshield of the car, by projecting the vehicular information in the direction of the front windshield. Furthermore, the display system of the present invention can be used for projecting various images, for example, on a shopwindow.
Hitherto, various head-up display system have been proposed. For example, there is provided a head-up display system where a reflection film, having a so-called half mirror property, is installed on the surface of a single glass plate or in the inside of a laminated glass. In this head-up display system, light is inevitably reflected from the inboard or outboard surface of the glass plate, as well as from the reflection film. This causes a problem of double image (ghost) phenomenon. To eliminate this problem, for example, Japanese Patent First Publication JP-A-2-141720 discloses a head-up display system having a phase film such as a xcex/2 film. This film serves to rotate the plane of polarization of polarized light having a particular wavelength of xcex. JP-A-2-294615 discloses another head-up display system having a transparent birefringent film, for example, of polyethylene terephthalate. U.S. Pat. No. 5,510,913, corresponding to JP-A-6-40271, discloses another display system having an optical rotatory film comprising a special liquid crystal polymer. JP-A-8-292393, corresponding to Japanese Patent Application 7-98878, discloses an automotive head-up display system where a polarized S-wave impinges on a laminated glass. This laminated glass has inboard and outboard glass plates and an interlayer film disposed therebetween. Furthermore, an optical rotatory film is disposed between the interlayer film and the inboard or outboard glass plate, and a semitransparent film is disposed on the inboard surface of the optical rotatory film. Still furthermore, a reflection preventive film is formed on the inboard glass plate. According to all of the above-mentioned publications, light from the display device impinges on the glass plate at an angle that is substantially equal to Brewster""s angle.
The inventors assume that, according to all of the above-mentioned conventional publications, the light ray of the center line (optical axis) of the display device is designed to be incident on a transparent platelike object (glass plate) at Brewster""s angle, but the other light rays except that of the center line are not. Therefore, we assume that the double image problem is not completely eliminated throughout the entire light rays from the display device in the above-mentioned conventional publications.
It is therefore an object of the present invention to provide a display system where the double image problem is substantially completely eliminated throughout the entire light rays of a display device.
According to the present invention, there is provided a display system where polarized light rays from a display device impinge on a platelike laminate at Brewster""s angle or emerge therefrom at an angle equal to Brewster""s angle, as will be clarified hereinafter. The platelike laminate is a combination of a transparent platelike object and a functional film that is an optical rotatory film or a semitransparent reflective film. The platelike object has front and back major surfaces opposed to each other. The display device has a polarizing member for polarizing the light rays of the display device into S-wave or P-wave light rays. The optical rotatory film of the platelike laminate rotates a plane of polarization of light rays. In other words, the optical rotatory film converts S-wave light rays into P-wave light rays, or alternatively converts P-wave light rays into S-wave light rays. The semitransparent reflective film of the platelike laminate reflects a part of light rays incident thereon and transmits the rest of the light rays therethrough.
A display system according to a first aspect of the present invention is characterized as follows. The display device throws light rays that are intended to be viewed by a viewer, against a front major surface of the platelike laminate, and its polarizing member polarizes the light rays into S-wave light rays. Furthermore, the optical rotatory film is formed on the front or back major surface of the platelike object or in an inside of the platelike object. The platelike laminate has a back major surface that is an interface between the platelike laminate and an air. The front major surface of the platelike laminate faces the display device such that a part of the S-wave light rays from the polarizing member is reflected from the front major surface of the platelike laminate towards the viewer and that the remainder of the S-wave light rays is transmitted in the platelike laminate and is converted by the optical rotatory film into P-wave light rays. The back major surface of the platelike laminate is curved such that substantially all of the P-wave light rays emerge from the back major surface of the platelike laminate into the air at an angle that is substantially equal to Brewster""s angle of one member of said optical rotatory film and said platelike object, which one member borders on the back major surface of the platelike laminate. In other words, when the optical rotatory film is formed on the back major surface of the platelike object, the above angle is substantially equal to Brewster""s angle of the optical rotatory film. In contrast, when the optical rotatory film is formed on the front major surface of the platelike object, the above angle is substantially equal to Brewster""s angle of the platelike object. The above angle is defined between a direction of propagation of the P-wave light ray in the air and a line that is perpendicular to the back major surface of the platelike laminate at a point of emergence of the P-wave light ray from the platelike laminate into the air.
A display system according to a second aspect of the present invention is characterized as follows. The optical rotatory film is formed on the front or back major surface of the platelike object or in an inside of the platelike object. The display device throws light rays that are intended to be viewed by a viewer, against the front major surface of the platelike laminate, and its polarizing member polarizes the light rays into P-wave light rays. The front major surface of the platelike laminate is curved such that substantially all of the P-wave light rays from the polarizing member are incident on the front major surface of the platelike laminate at Brewster""s angle.
A display system according to a third aspect of the present invention is characterized as follows. The display device throws light rays that are intended to be viewed by a viewer, against the front major surface of the platelike object, and its polarizing member polarizes the light rays into P-wave light rays. The semitransparent film is formed on the back major surface of the platelike object. The front major surface of the platelike object is curved such that substantially all of the P-wave light rays from the polarizing member are incident on the front major surface at Brewster""s angle of the platelike object.
A display system according to a fourth aspect of the present invention is characterized as follows. The semitransparent reflective film is formed on the front major surface of the platelike object. The display device throws light rays that are intended to be viewed by a viewer, against the reflective film, and its polarizing member polarizes the light rays into P-wave light rays. The reflective film faces the display device such that a part of the P-wave light rays from the polarizing member is reflected from the reflective film towards the viewer and that the remainder of the P-wave light rays is transmitted in the reflective film and then in the platelike object. The back major surface of the platelike object is curved such that substantially all of the remainder of the P-wave light rays emerge from the back major surface thereof into the air at an angle that is substantially equal to Brewster""s angle of the platelike object. This angle is defined in the same manner as in the first aspect of the invention.
Thus, according to the present invention, the double image problem does not at all arise.